#define _CRT_SECURE_NO_WARNINGS 1
#include<stdio.h>
int operate(unsigned int n);
int main()
{
	int n = 0;
	int ret = 0;
	scanf("%d", &n);
	ret = operate(n);
	printf("%d", ret);
	return 0;
}
int operate(unsigned int n)
{
	if (n == 0)
	{
		return 1;
	}
	return n * operate(n - 1);
}